File handling is awesome

--Add OPEN to allow the user to open file handles. Passing a mode is
  really ugly so I don't do that but then I have trouble with
  overwriting the file vs appending to it on writes. I've settled with
  append for now but that may change.
--Allow READ to take a second argument, a number, which jumps the file
  to the start of the nth line. 0 is the first line. If the number is
  negative, then it jumps to the (0 - n)th line counting from the
  bottom, with -1 being the last line.
--Simplify WRITE greatly since it doesn't need to return a char*
  holding the string that it just output.